Electrodes having a metallic, liquid-cooled, upper section and a lower section of a consumable material, preferably graphite, attached to the upper section, are generally known as combination electrodes. European patent application No. 80106581.4 describes such a combination electrode. Having demonstrated utility, such electrodes are replacing more conventional graphite electrodes to an increasing degree.
Problems of how to connect such combination electrodes to necessary facilities, such as electrical power or coolant, and how to attach or insert the electrodes into an electrode support at the electric arc furnace have not yet been solved satisfactorily. At present, conventional electrode support arms are simply modified to fit a combination electrode without departing from an established design concept. Typically, on the side of a combination electrode, conventional, vertically movable, swivelling electrode support arms encompass radially movable clamping jaws between which the electrode to be employed is inserted by means of a hoist. The clamping jaws are consequently pressed against the sheath area of the electrode. In this way the electrode is supportively fastened in a positive manner. At the same time the clamping jaws serve as an electrical contact arrangement for the transition of electric current to current-carrying components of the electrode. Where graphite electrodes are used, the clamping jaws encompass the graphite column at the upper end, while the clamping jaws for combination electrodes encompass the metallic section of the combination electrode directly or contact the metallic section via conductive intermediate elements.
Where combination electrodes are used, it is relatively complicated to use conventional electrode support arms, since, in addition to the usual handling operations, it is necessary to connect a liquid coolant system. Connection is achieved in a separate operation as the electrode is set to work. On the other hand, such a coolant system requires disconnection in a separate operation when the electrode in question is replaced. These operations consume not only significant time but are also difficult, being carried out under extreme working conditions upon or adjacent the operating furnace.